Short diagnosis of development of a tropic surge, cut-off low and AR features

December 2, 2014

Storm surge summary (slide 10; M. Ralph)

CW3E director Marty Ralph provides a short diagnosis of an interesting case with a variety of features coming together to generate very large IWV in this currently landfalling storm.

Dr. Ralph notes “This could be a useful event to diagnose more deeply given its relevance to many things we are working on, and the debates about AR, cut-off low, tropical moisture exports, etc. The IVT perspective needs to be explored as well, but the IWV features are quite telling. Jay Cordeira had shared a brief synopsis including a cross-section from GFS that showed the vapor transport over LA maximized at about 3.5 km, which may be more like a ‘tropical moisture export’ structure (Knippertz et al).”

The attached ppt includes an isochrone analysis of the northern edge of the tropical water vapor reservoir (using 4 cm IWV – summary shown above and in slide 10) and its landfall (as seen in the GPS-Met network – slide 11). Also, the snow levels are well-observed with the new SLR network and shows strong north-south variation (slide 12)..

Forecasts are available from the California Nevada River Forecast Center (CNRFC): click here for precipitation forecasts..

Forecasts are also available from the weather service forecast office of the National Weather Service in San Diego: please click here.